Recently I bought a Field View Mill to convert to a lighthouse (at that time there wasn't a Sylvanian lighthouse). 
1. First step- take the top off the mill
There is a lovely groove which makes the conversion easier.
2. Second step, cut a circle the size of the base of the blue observatory.
3. Cut a straight piece approximately 11cm wide & long enough to wrap around the circle.
4. Glue together & place on top story. Make sure it sits snuggly inside the groove.
It's starting to take shape.
5. Cut the style of lighthouse lantern that you want.
Testing it to see if it works.
6. Paint it your desired colour.
This is my inspiration.
